Problem: Simplify the following expression: $k = \dfrac{9}{5n} + \dfrac{1}{2n}$
Explanation: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5n$ and $2n$ $\lcm(5n, 2n) = 10n$ $ k = \dfrac{2}{2} \cdot \dfrac{9}{5n} + \dfrac{5}{5} \cdot \dfrac{1}{2n} $ $k = \dfrac{18}{10n} + \dfrac{5}{10n}$ $k = \dfrac{18 +5}{10n}$ $k = \dfrac{23}{10n}$